1. Field of the Invention
The present invention relates to compressors.
2. Description of the Related Art
In order to reduce the carbon dioxide emissions, electric vehicles using a fuel cell have been developed. The fuel cell generates electric power by an electrochemical reaction between oxygen supplied to a cathode and hydrogen supplied to an anode. In an electric vehicle, in order to supply oxygen to the cathode of the fuel cell, oxygen in air compressed and supplied by a compressor is used.
However, the compressor has a problem in that various noises are generated from an air inlet side and a discharge outlet side. In addition, in electric vehicles on which a fuel cell is mounted, in view of reaction temperature and heat resistance of the fuel cell, it is necessary to reduce the temperature of the air discharged from the compressor, and a heat exchanger such as an intercooler or the like is provided to reduce the temperature of the discharged air. However, a large number of auxiliaries are mounted in an electric vehicle, and hence there is a problem that it is difficult to secure a mounting space.
Japanese Patent Application Laid-open No. 2003-184767,, for example, describes a screw compressor having two rotors to be mounted on a fuel cell vehicle in which there is provided a silencing and cooling device having a silencing function for reducing noise from the discharge outlet side and a function for cooling discharged fluid (air). In Japanese Patent Application Laid-open No. 2003-184767,, a cover which internally forms an additional space is attached to the outside of the housing of a compressor, and the additional space is formed between two planes which extend orthogonal to a plane connecting the two central axes of the two rotors that are in parallel with each other, and further the two planes pass through the two individual central axes. That is, the additional space is formed at a position where a valley is formed by the pair of rotors in a part of the housing.
Further, the additional space forms an inlet-side space connected to a discharge port of a space where the rotors are accommodated and an exit-side space connected to a discharge outlet serving as an opening of the cover. Furthermore, the inlet-side space and the exit-side space are connected via a plurality of heat exchanging tubes provided in the additional space. Moreover, heat exchanging flow paths are formed in the plurality of heat exchanging tubes, and cooling water paths are formed between the plurality of heat exchanging tubes. In addition, heat exchanging fins attached to the outside of the heat exchanging tubes protrude into the cooling water paths. With this arrangement, when a fluid such as air discharged into the additional space from the discharge port flows from the inlet-side space to the exit-side space, the fluid is subject to a silencing action with its discharge pulsations being damped, and also is subject to a cooling action by effecting heat exchange with the cooling water in the cooling water paths while flowing in the narrowed heat exchanging flow paths formed in the heat exchanging tubes.
However, in the compressor in Japanese Patent Application Laid-open No. 2003-184767,, since the cover is attached to the housing as a separate member, the housing and the cover generate separate vibrations by the mechanical vibration generated by the compressor so that a problem arises that the generated vibration causes the cover to generate a noise, or that the generated vibration may deform the cover and the deformed portion vibrates to generate a noise.